- #1

Lucille

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## Homework Statement

A simple way to build a bandpass filter is to filter the output of an RC highpass filter with an RC lowpass filter, as shown on the left in the diagram below. The isolation buffer is a circuit element that keeps the two circuits isolated so they behave as they would on their own. The (highly idealized) response of the circuit is shown on the right, where fL and fH are the low and high cutoff frequencies.

a) Assume fL is given by the equation for the cutoff frequency of a high pass filter, and fH is given by the equation for the cutoff frequency of a low pass filter. If the value of the resistors is 10 kOhm what should the value of the capacitors be if you were building an audio filter to allow vocal frequencies between fL = 80 Hz and fH = 1100Hz.

b) Assuming the high frequency behavior of the filter is described entirely by the response of the low pass filter, what would the gain, Vout/Vin, be at 10 000 Hz?

Image available at http://www.chegg.com/homework-help/questions-and-answers/simple-way-build-bandpass-filter-filter-output-rc-highpass-filter-rc-lowpass-filter-shown--q3608656

## Homework Equations

f_c = 1/(RC*2Pi)

Vout/Vin = 1/ sqrt(1+(RwC)^2)

## The Attempt at a Solution

a) C = 1/(2pi*f*R) -- do I calculate two different capacitance values?

so C1 = 1.99*10^-7 and C2 = 1.45*10^-8

b) Using C2 and plugging into the equation gives 0.568